I'm posting this over to Adobe as well, but I suspect I might get an answer more quickly here.

Spec sheets for a number of clients my team is creating content for require ProRes 422 renders at 8bpc and millions of colors. Our comps have been set-up with the correct specs and our output modules reflect the spec sheets exactly. However, during our QA process, when bringing our MOVs back into AE to inspect their settings, the project window shows them as having Trillions of Colors.

These renders have no alpha channel (422 doesn't support it anyway), the settings have been triple checked to ensure project depth is set to 8bpc and the Output module settings have Millions of Colors specified in depth. We're worried that the client may use the same method to check the files and kick them back for being off-spec so I'm asking around to see if there's something we're doing incorrectly, a step we're missing or if this is some sort of bug in AE.

My only relief in all this is that when I check the movie inspector in Quicktime, I do indeed see Millions of Colors.

Not as of yet. I kinda fear Dave LaRonde response if I've missed something entirely obvious.

I got a semi-thorough response on the Adobe forums that boiled down to "Well, the codec is 10bit, no matter what, so it's color palette is the color palette no matter how you tell AE to render it". I.E. it is what it is. AE is saying it has trillions (which isn't exactly true) and Quicktime's movie inspector says it has millions (which isn't exactly true either).

Some further reading on what bit depth actually is cleared things up for me though. 8 bit color is literally eight bits of data for each of the RGB values on a single pixel. With 256 possible, 8 bit binary numbers, you end up with 256 possible shades for each RGB value ultimately equaling 16.7 million colors. 10 bit color depth means that you can get 1024 shades of each color. 1024Rx1024Gx1024B = over a billion.

So, ProRes (which technically doesn't even use RGB, but Y’, CB, and CR) being the 10bit codec that it is, will always output to this billions. I'm assuming that when AE reads the file in, it rounds up to the generic "trillions of colors" readout, whereas Quicktime just doesn't know any better and defaults to millions.

We have quicktime on all of our computers at work..however only 2 of them can render out for quicktime..Some kind of bug that prohibits most of the computers from going to quicktime in after effects and in media encoder..could be related to your problem